In commercial aviation, it is necessary to dispose of unwanted fluids and solids. Currently, most commercial aircraft are equipped with galley and lavatory sinks; however, these sinks are primarily intended for the disposal of fluid waste only as they are connected to small diameter drain lines and drain primarily by gravity. These drains generally range from about one half to one inch in diameter and terminate at an aircraft drain mast for exhaustion to the atmosphere. Unfortunately, such sink systems are limited in their ability to dispose of more viscous liquid or solid waste products. Current sinks are also prone to blockage due to drainage of liquids that solidify when combined in the drain system.
Currently, disposal of most non-liquid wastes is accomplished through conventional vacuum systems for toilets and waste disposal units. While generally effective for disposing of solid, liquid and slurry food wastes, implementing one of the conventional vacuum toilet or waste disposal unit designs requires incorporation of a separate unit in addition to the sink. While these designs provide an alternate location for solid waste disposal, they do not eliminate the potential for clogged sink drain lines.
A problem with incorporating current galley sink designs into a vacuum waste system relates to noise. A loud flushing sound is created when the flush valve opens and the differential pressure across it forcefully draws the waste down the drain. To reduce the noise during drainage, a by-pass line can be installed to control the amount of airflow passing through the sink bowl. The bypass line reduces the noise but also reduces the amount of vacuum available help drain the sink.
The disadvantages associated with current aircraft sink systems have made it apparent that a new technique for removing waste from an airplane sink is needed. The new technique should minimize noise onboard the aircraft and allow system clogs to be flushed out.